1. Field of the Invention
The present invention generally relates to an on-demand multimedia server and more particularly to a server, responsive to a request from one of consuming devices, for serving requested multimedia information in a format adapted to the requesting consuming device.
2. Description of the Prior Art
Some of the terms used herein will be first defined for the sake of better understanding the following description. Multimedia information of each of a plurality of multimedia applications is a compiled set of single-media data such as video, animation, graphics, sound, text and computer programs, which are each called a xe2x80x9cmaterial.xe2x80x9d Each material is represented by xe2x80x9cmaterial dataxe2x80x9d contained in a xe2x80x9cmaterial file.xe2x80x9d Information on a specific material (file) including the file name and attributes of the material data is referred to as xe2x80x9cmaterial information.xe2x80x9d The data format of material data or file is referred to as xe2x80x9cmaterial format,xe2x80x9d which may be, for example, an MPEG 1 (Moving Picture Coding Experts Group 1) format in case of video, a JPEG (Joint Photographic Coding Experts Group) format in case of graphics and so forth. Each of the multimedia applications generally comprises some kinds of material data constituting the multimedia application and xe2x80x9cscenario dataxe2x80x9d which describes how each material plays its role in the application (e.g., from when a first material, for example a video, is to be replayed; when and in what part of the screen a second material, for example a still picture, is to be displayed; and so on). Information on a specific scenario (file) including the file name and attributes of the scenario is referred to as xe2x80x9cscenario information.xe2x80x9d
There are various kinds of so-called multimedia service systems. In such a system, each of the multimedia applications is prepared by preparing material data used in the application and creating scenario data for the application in a multimedia source device and by storing the material data and the scenario data in a multimedia server. Multimedia information is provided to the user in a multimedia consuming device or play-back device by the multimedia server serving material data and scenario data for a specified multimedia application to the consuming device, which uses the served data to reproduce or play back the specified multimedia application. In this way, prepared material data and scenario data are stored and served as they are.
As described above, there are various types of materials such as video, animation, graphics, sound, text and computer programs. There may be also various data formats even for the same type of material. Specifically, data formats for a material type of, e.g., video (or moving picture) include DV, MPEG 2, MPEG 1, etc., and there are variety of data formats for a material type of, e.g., graphics (or still picture) including JPEG, BMP (the standard bit-mapped graphics format used in the Windows environment), etc.
If two materials are in different formats even though the materials are of an identical material type, reproduction of the two materials stored in the different format needs different play-back devices with respective structures and functions. To take an example, a play-back device for playing back moving picture data in the DV format has a function of extracting an image signal from DV format data. Similarly, a play-back device for playing back moving picture data in the MPEG 1 format has a function of extracting an image signal from MPEG 1 format data. These two functions are different from each other and neither function includes the other.
Further, in order to play back moving picture of a bit rate (which is determined by the frame size, the frame frequency and the resolution of the moving picture) exceeding a certain level, it is necessary to realize, by means of hardware, at least a part of the function of extracting an image signal from moving picture data regardless of whichever format the moving picture data is in. For this reason, it is not a practical solution to provide each play-back device with play-back functions for different data format.
It is therefore an object of the invention to provide a multimedia information server which serves each of consuming devices (or client play-back devices) with a multimedia application in a format adapted to the consuming device.
In a multimedia information service system, a server is supplied with multimedia applications each comprising a plurality of kinds of materials and a scenario which defines a role of each material. The server registers or stores each (multimedia) application in response to a reception thereof (registration operation) and, in response to a request from one of a plurality of consuming devices or clients, serves a requested one of the applications in a format with which the requesting client can deal with respect to materials of a certain kind (e.g., moving picture materials) among the plurality of kinds (service operation). In accordance with one aspect of the invention, the server converts an input (or original) format of the certain kind of materials of at least one of the applications into at least one of target formats associated with the input format either in the registration operation or in the serving, or service operation (material conversion). Each scenario of the at least one application (which scenario is for said input format) is converted into at least one scenario of that application in the target formats, either in the registration operation or in the service operation (scenario conversion). In response to a request for one of the applications, the server serves the requesting one of the consuming devices with at least a scenario of the requested application which scenario has been adapted to the format with which the requesting consuming device can deal. This enables every consuming device to consume any of the multimedia applications stored in the server regardless of the material format with which the consuming device can operate with respect to a certain kind of material.
In one specific embodiment of the invention, both of the material conversion and the scenario conversion are performed in the registration operation. This enables a quick response in service operation but will need a mass storage device of the largest capacity.
In another specific embodiment of the invention, the material conversion (which takes more time than the scenario conversion) is performed in the registration operation and the scenario conversion is performed in the service operation. This enables a relatively quick response in service operation with a mass storage device of a relatively large capacity.
In further specific embodiment of the invention, both of the material conversion and the scenario conversion are performed in service operation. This can save the capacity of the mass storage device but will cause the service operation to take time.
In still further specific embodiment of the invention, materials which take more time for format conversion are converted in the registration operation, and the scenario of requested application and, if the materials for the requested application have not been converted, such materials are converted in the service operation. In this case, the server will afford a quicker service at the cost of moderate capacity of the mass storage device.
The input material formats may be limited to master data formats, i.e., data formats that each contains the maximum quantity of information in all the data formats for one category of materials, and material formats available for service may be obtained by converting the master data formats. By doing this, the server can provide multimedia information of further higher quality.